Circuit arrangement with automatic starting and amplitude stabilization, especially for small electronic clocks and watches

ABSTRACT

A circuit arrangement, especially for small electronic clocks and electronic watches, which provides for automatic starting of the oscillator of the watch or clock upon energization of the circuit and which provides for amplitude stabilizing during the operation of the watch or clock.

United States Patent [191 Reich [111 3,805,510 [451 Apr. 23, 1974 CIRCUIT ARRANGEMENT WITH AUTOMATIC STARTING AND AMPLITUDE STABILIZATION, ESPECIALLY FOR SMALL ELECTRONIC CLOCKS AND WATCHES Inventor: Joachim Reich, Via-Noseda-S, CH-

6977 Ruvigliana, Switzerland Filed: Dec. 27, 1972 Appl. No.: 318,838

Foreign Application Priority Data Dec. 30, 1971 Switzerland 19262/71 U.S. C1. 58/23 A, 58/28 R, 318/133 Int. Cl G04c 3/00, G040 3/04 Field of Search 58/28 R, 28 A, 28 B, 23 A, 58/23 TF; 318/133; 331/182, 183, 109, 110

[56] References Cited UNITED STATES PATENTS 3,593,200 7/1971 Reich 331/116 3,605,401 9/1971 Reich 58/28 A Primary Examiner'-Richard B. Wilkinson Assistant Examiner- Edith Simmons J ackmon Attorney, Agent, or Firm-Melvin A. Crosby 57 ABSTRACT 7 Claims, 1 Drawing Figure cillator having a magnet system thereon and mounted adjacent the oscillator, so as to cooperate with the magnet system, is a stationary coil system consisting of an exciting coil and a driving coil. The circuit arrangement in which the exciting coil and driving coil are incorporated is generally in the form of a transistor amplifier, or a blocking oscillator, together with a power source in the form of a miniature battery.

When the oscillator moves relative to the coil system, a voltage pulse is developed in the exciting coil which will cause the transistor to go to conduction and a pulse of current will then pass through the transistor and the driving coil and exert a driving impulse on the oscillator to cause it to oscillate and, therefore, to actuate the clock mechanism.

Amplitude stabilization is important in respect of such circuit arrangements in order to provide for isochronous operation and also to take into account the voltage of the battery supplying the power to the circuit will vary rather widely from the time the battery is fresh until the time the battery is about exhausted. One of the simplest forms of circuit providing for stabilization consists of an arrangement for switching a diode in parallel with the driving coil, preferably a Zener diode, or several diodes in series. A

With this arrangement the driving voltage is kept constant but a loss occurs because of the current flow through the path paralleling the driving coil. This form of circuit, while it provides for stabilization, wastes too much current for small clocks and also for watches.

In another known stabilization circuit, diodes are in series with the exciter coil. This circuit has the advantage that the current drain on the battery is not increased but, due to the characteristics of the diodes, the stabilization is effective only up to the time the battery voltage is reduced to about 1.3 volts. At voltages for about 1.3 volts down to about 1.1 volt, at which latter point the battery is considered exhausted, little stabilization occurs. The amplitude deviation with the last mentioned arrangement will still be about 20 degrees,-

which istoo great a variation in amplitude to obtain proper isochronous operation.

Still a further stabilization arrangement involves transistor regulation circuits, but in these also the stabilization limit is at about 1.25 volts and at values lower than which sort of clocks and watches are equipped with mercury batteries, the degree of stabilization provided by the arrangements described above is insufficient.

2 With the foregoing in mind, a primary objective of the present invention is the provision of a circuit atrangement, especially for electronic watches and small clocks wherein the degree of stabilization is significantly improved over what has been achieved in known GENERAL ARRANGEMENT In the circuit arrangement of the present invention, a transistor is provided having a collector connected to one pole of a battery. The collector is also connected to the base of the transistor with the interposition of a series of circuit which consist of a first resistor, a second resistor, and the exciter coil. Furthermore, a first condensor is placed between the emitter of the transistor and the juncture of the aforementioned first and second resistors and with the emitter furthermore being connected through the driving coil with the other pole of the battery.

Still further, a series of diodes arranged in series, are connected in parallel with the above mentioned condensor and driving coil.

The above mentioned first resistor and'the condensor are so selected that, between two consecutive driving impulses generated in the driving coil, the condensor can be charged up at the most to the base potential of the transistor at which the transistor will, go to conduction.

The second resistor, namely the resistor that is serially arranged with the exciter coil, is selected so that, at the earliest, the full exciter impulse is effective on the base of the transistor when the battery voltage is at the lowest allowable value.

The degree of stabilization by the circuit arrangement of the present invention is less thanabout one per cent compared to about ten per cent obtained by known stabilizing circuits according to the prior art. In particular, the additional current drawn for obtaining the stabilization effect realized by the practice of the present invention is less than about five "per cent of the rated current consumption so that the present inven' tion may be advantageously employed for wrist watches and small clocks. The voltage of a mercury cell of the type used with electronic watches, clocks, ranges from about 1.45 volts for fresh battery to about 1.1 volts for a spent battery. 1

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings somewhat more in detail, the transistor T illustrated is an NPN transistor with the collector connected to the plus pole of the battery B. The emitter of the transistor is connected through driving coil A, with the minus pole of the battery B, while taining condenser C1 and driving coil A. A further condenser C2 is connected in parallel with resistor R1 and provides for the attenuation of blocking oscillation.

The described circuit operates as follows: When the circuit is first energized, condenser Cl becomes charged up by current flowing through resistor R1, which may be about 1,000 ohms to about 100,000 ohms, until the gating voltage of transistor T has been reached, whereupon the transistor goes conductive and current will flow from the battery through the collector-emitter path of transistor T and then through the driving coil A back to the battery. This will deliver a driving impulse to the oscillator of the watch or clock to set the oscillator in motion while simultaneously the charge on condenser C1 will be reversed because the emitter of the transistor will go from negative to positive when the transistor goes conductive.

When the oscillator is in operation and is oscillating at normal amplitude, condenser C1 is charged partially only in the interval between successive driving pulses and serves as an auxiliary voltage source for the exciting voltage which is released by the exciting coil E to the base-emitter circuit of the transistor.

The width of the impulse to driving coil A depends, of course, on the duration of the exciter coil impulse. During the exciting coil impulse a current flows in a closed circuit consisting of the exciter coil E, the base of the transistor, the emitterof the transistor, the first condenser Cl, and the second resistor R2. The duration of the exciter impulse is dictated by the geometry of the exciter coil and of the magnet system, and the height, or strength, of the exciter pulse is dictated by the number of windings in the exciter coil and the strength of the magnetic field of the magnetic system.

By the second resistor R2, the circuit constant becomes changed in the sense of an increase, that is to say, that a current will flow in the circuit for a longer time and that the amplitude thereof becomes greater.

Because of the diode combination D, which, in the case of a silicon transistor, consists of three diodes and, in the case of a germanium transistor, consists of two diodes, a part of the voltage which is developed at point V at the moment the transistor is switched on will be caused to flow through the diode branch D to the minus.

pole of battery B.

The voltage which arises at point V which will correspond to the sum of the gating voltage of transistor T and from the voltage supplied to the emitter, is the voltage which causes current to flow through the diode branch. This voltage would thus be about 2.05 volts for a fresh mercury battery, and about 1.7 volts for a mercury battery on the point of depletion.

As the gating voltage of the diodes is selected to be just slightly above the gating voltage of the transistor, and the diode path has only a few ohms, the impulse released by the emitter for the condenser Cl is immediately conducted across the diode combination D toward the minus pole of the battery so that the cendensor C1, the reversal of the charge on which is ordinarily determined by the resistance of the coil and its capacitance gets reversed in a much smaller time. The time for the reversal of the charge on condenser C1 is shorter as the current which flows through the diode combination increases. The drive impulse developed by the transistor is thus rendered shorter. When the battery voltage drops, a portion only of the current flows through the diode combination and, in this manner, the time requiredfor the reversal of the charge of condenser Cl is extended.

In order to bring about that even under boundary conditions the stabilization conditions referred to obtain the resistor R2 is selected so that only at the smallest admissable operating voltage of the battery B, namely, at about 1.1 volts for a mercury battery, is all of the impulse generated by the exciter coil released for biasing the transistor toward conduction. Resistor R2, for example, might vary from about ohms to about 1,000 ohms. As a matter of fact, the value of resistor R2, if chosen correctly, can bring about that the amplitude of the oscillator increases as the battery voltage decreases. This would not, of course, be usefulv for stabilization, per se, but could be useful for use in respect of temperature compensation, if necessary.

All of the stabilization of circuits of the prior art have a definite negative temperature coefficient which can be compensated'by the circuit arrangement according to the present invention by the selection of the resistor R2.

The gate voltage of the diodes of the diode branch D changes with temperature so that the charge reversal time of the condenser C1 will also change with temperature and this, in turn, also causes the drive impulse time to change. By the selection of the proper resistor at R2, the circuit can be made constant by the provision of slightly excessive compensation. Resistor R2 in this case serves the purpose of stabilizing the time required for the reversal of the charge on condenser Cl at the smallest possible operating voltage of the battery B so that it will coincide accurately with the length of the exciting impulse, or that it may actually be longer than the exciting impulse which leads to the above mentioned excessive compensation which simultaneously serves as a temperature compensation.

It will be understood that the circuit arrangement as shown with an NPN transistor, could, of course, be effective with a PNP transistor merely by reversing the polarity of the battery and the diode branch D.

Modifications may be made within the scope of the appended claims.

What is claimed is:

1. In a stabilized circuit arrangement for self starting electronic clocks and watches in which an oscillator having a magnet system thereon is actuated by the circuit arrangement; a coil system comprising an exciting coil and a driving coil, a transistor having collector, emitter and base terminals, a battery having one pole connected to said collector terminal and the other pole connected to one end of said driving coil, the other end of said driving coil being connected to said emitter terminals, one end of said exciter coil being connected to said base terminal, a first resistor having one end connected to said collector terminal, a second resistor having one end connected to the other end of said first resistor and the other end connected to the other end of said exciter coil, a first condenser having one end connected to the juncture of said resistors and the other end connected to said emitter terminal, and a branch consisting of at least two diodes in series connected between the juncture of said resistors and said other pole of said battery, said first condenser charging through said first resistor when the circuit is initially energized with a fresh battery to that potential which will cause the transistor to go to conduction and thereby start the oscillator and thereafter between successive impulses developed in said exciter coil during operation of the oscillator charging to a lesser amount which is additive to the voltage developed in said exciter coil, said diodes conducting current via said second resistor due to the voltage developed in said exciter coil during operation of said oscillator and the said current diminishing toward zero as said battery approaches the spent voltage thereof.

2. A circuit arrangement according to claim 1 in which said transistor is a silicon transistor and said diode branch comprises three diodes in series.

3. A circuit arrangement according to claim 1 in which said transistor is a germanium transistor and said diode branch comprises two diodes in series.

4. A circuit arrangement according to claim 1 which includes a second condenser in parallel with said first resistor.

5. A circuit arrangement according to claim 1 in which said second resistor has a value between about ohms and 1,000 ohms.

6. A circuit arrangement according to claim 1 in which said first resistor has a value between about l,000 ohms and 100,000 ohms.

7. A circuit arrangement according to claim 1 in which said first resistor has a value between about 1,000 ohms and 100,000 ohms and said second resistor has a value between about 100 ohms and 1,000 ohms. k k 

1. In a stabilized circuit arrangement for self starting electronic clocks and watches in which an oscillator having a magnet system thereon is actuated by the circuit arrangement; a coil system comprising an exciting coil and a driving coil, a transistor having collector, emitter and base terminals, a battery having one pole connected to said collector terminal and the other pole connected to one end of said driving coil, the other end of said driving coil being connected to said emitter terminals, one end of said exciter coil being connected to said base terminal, a first resistor having one end connected to said collector terminal, a second resistor having one end connected to the other end of said first resistor and the other end connected to the other end of said exciter coil, a first condenser having one end connected to the juncture of said resistors and the other end connected to said emitter terminal, and a branch consisting of at least two diodes in series connected between the juncture of said resistors and said other pole of said battery, said first condensor charging through said first resistor when the circuit is initially energized with a fresh battery to that potential which will cause the transistor to go to conduction and thereby start the oscillator and thereafter between successive impulses developed in said exciter coil during operation of the oscillator charging to a lesser amount which is additive to the voltage developed in said exciter coil, said diodes conducting current via said second resistor due to the voltage developed in said exciter coil during operation of said oscillator and the said current diminishing toward zero as said battery approaches the spent voltage thereof.
 2. A circuit arrangement according to claim 1 in which said transistor is a silicon transistor and said diode branch comprises three diodes in series.
 3. A circuit arrangement according to claim 1 in which said transistor is a germanium transistor and said diode branch comprises two diodes in series.
 4. A circuit arrangement according to claim 1 which includes a second condenser in parallel with said first resistor.
 5. A circuit arrangement according to claim 1 in which said second resistor has a value between about 100 ohms and 1,000 ohms.
 6. A circuit arrangement according to claim 1 in which said first resistor has a value between about 1,000 ohms and 100,000 ohms.
 7. A circuit arrangement according to claim 1 in which said first resistor has a value between about 1,000 ohms and 100,000 ohms and said second resistor has a value between about 100 ohms and 1,000 ohms. 